The discovery of X-rays by Rontgen in 1895, and of radioactivity by Becquerel in 1896, was followed by an early appreciation of both the damaging and therapeutic effects of ionizing and ultraviolet radiation (Including genetic effects, for which Muller later received the Nobel Prize). From this emerged radiation research, a multi-disciplinary field embracing physics, chemistry, biology, and medicine, all of which are involved in our ultimate understanding of radiobiological damage and radiotherapy. The Radiation Research Society was formed in the USA in 1952 and was followed soon after by the formation of societies in Great Britain, the Netherlands, Sweden, Poland, the European Society (including Germany, France, Italy, and others), Japan and Israel. These societies now form the International Association for Radiation Research (IARR), a component of the International Union of the Biological Sciences. The 1st International Congress of Radiation Research was held in Burlington, Vermont in 1958 and since then, at 4-year intervals, international congresses sponsored by IARR have been held in England, Italy, and France. The 5th Congress was chosen to be in the U.S. at the invitation of the Radiation Research Society to the IARR in 1968. Seattle was selected as the site because of its outstanding meeting facilities in the Seattle Center, the additional availability of the facilities at the University of Washington, and the strong invitation of a Local Committee. The multidisciplinary nature of the subject renders these international meetings especially valuable. Physicists, chemists, biologists, and physicians, together with many others from subspecialties involved in radiation studies, meet to discuss their progress. It is appropriate that the U.S. be the venue of the 5th international meeting, because of its leading role in the development of atomic energy, in radiation research, and in the expansion of interest to other environmental hazards. This will be the first international meeting here in this field in 16 years and the Radiation Research Society will forego its annual meeting in favor of the International Congress. All Americans interested in the field are expected to attend and outstanding scientists from all over the world will participate. The meeting will be important international scientific event and a significant milestone (Text Truncated - Exceeds Capacity)